# angles - equation 2

You know that opposite angles are equal to one another. So the angle of the bottom left-hand corner of the paralleogram is also B. Now, since this B and 3a lie on a line, you know that: $3a + B = 180$
Also, you know that adjacent angles of a parallelogram are supplementary (they add up to 180). So you have that $a + 82 + B = 180$